plants

• Land plants


  • Autotrophs
  • Movement onto land by algal ancestors provided: unfiltered sun, more CO2, nutrient-rich soil, less herbivores and pathogens
  • Since 500 mya, land plants have diversified into >300,000 living species
  • Plants supply oxygen and are the ultimate source of food eaten by land animals
• Derived traits of plants

  • Alternation of generations
  • Spores produced in sporangia
  • Apical meristems

  
• Alternation of generations

  • Plants contain two different multicellular forms in their life cycle
  • Sporophyte (diploid) produces spores by meiosis
  • Gametophyte (haploid) produces gametes by mitosis

  
• Spores produced in sporangia

  • Sporophyte (diploid) produces spores by meiosis
  • Spores are produced in sporangia
  • Diploid sporocytes undergo meiosis to produce haploid spores
  • Spore walls made of sporopollenin

  
• Apical meristems

  Sites of continual growth

  
• Bryophytes

  • Life cycle dominated by gametophyte (haploid)
  • Bryophytes include three phyla of herbaceous (nonwoody) plants: Marchantiophyta (Liverworts), Anthocerophyta (Hornworts), Bryophyta (Mosses)

  
• Life cycles with dominant gametophyte

  • Haploid gametophyte grows from spores - "dominant" form
  • Gametes are produced in structures called gametangia via mitosis
  • During wet conditions, sperm produced in antheridia swim to eggs produced in archegonia
  • Depending on the species, antheridia and archegonia may be housed on a single gametophyte or separate male and female gametophytes
  • The zygote will grow into a mature diploid sporophyte - "reduced" form, completely dependent on the gametophyte for nutrients/energy, produces spores in sporangia, diploid sporocytes undergo meiosis to produce haploid spores
• Liverworts

  • moss

  
• Evolution of vascular tissues allowed plants to grow tall

  Living vascular plants are characterized by: Life cycles with dominant sporophytes, Vascular tissues (xylem and phloem), Well-developed roots and leaves

  
• Life cycles with dominant sporophytes

  • Haploid spores produce mature gametophytes - reduced (2-5mm), Depending on the species antheridia and archegonia may be housed on a single gametophyte or separate male and female gametophytes
  • During wet conditions, sperm produced in the antheridia swim to the egg housed in the archegonia
  • The zygote will grow into a mature diploid sporophyte - "dominant" form, much larger than the gametophyte, sporangia house sporocytes that undergo meiosis to produce haploid spores

  
• Vascular tissues: xylem and phloem

  • Xylem: conducts water and minerals, consists of dead cells (e.g. tracheids and vessel elements), cell walls strengthened by lignin
  • Phloem: distributes sugars, amino acids, and other organic products, consists of living cells

  
• Roots and leaves

  • Roots: organs that anchor vascular plants, enable plants to absorb water and nutrients from the soil
  • Leaves: organs that increase the surface area of vascular plants, capture solar energy used in photosynthesis
• Seedless vascular plants

  Two phyla: Lycophyta (club mosses, spike mosses, and quillworts), Monilophyta (ferns, horsetails, and whisk ferns)